A fuel cell is an electric generator that is comprised of at least a solid or liquid electrolyte, and two electrodes consisting of an anode and a cathode which induce an electrochemical reaction. It directly converts a chemical energy of the fuel into an electric energy with a high efficiency. As the fuel, there is the used of fossil fuels, hydrogen that has been chemically converted from water, methanol, alkali hydride, hydrazine which are liquid or solution in the normal environments, or dimethyl ether which is a pressurized liquidized gas. As an oxidizer gas, air or oxygen gas is used.
The fuel is electromechanically oxidized in the anode, and oxygen is reduced in the cathode, to thereby produce an electric potential difference between both of those electrodes. In this situation, when a load is applied between both of those electrodes as an external circuit, ionic migration is generated in the electrolyte, and an electric energy is provided for the external load. Various fuel cells are greatly expected as a large-scaled generator system as substitute for fire power equipment, a small-scaled diffusion type cogeneration system, or an electric vehicle power supply as substitute for an engine dynamo. Thus, the fuel cells have been actively developed so as to put into practical use.
Among those fuel cells, attention has been paid to a direct methanol fuel cell (DMFC), a metal hydride fuel cell, and a hydrazine fuel cell as effective fuel cells for a downsized mobile or portable power supply because the volume energy density of the fuel is high. In particular, DMFC employing methanol that is readily dealt with and expected to be produced from biomass in the near future as fuel is an ideal power system.
Japanese Patent Laid-Open No. 2002-216782 discloses a hybrid system having a fuel cell and plural secondary cells that are connected in parallel with the fuel cell.
The fuel cell has a propensity that it takes a long time until stably supplying an electric power required for a load (for example, electronic equipment) after starting the fuel cell because the fuel cell is a generator that converts a chemical energy into an electric power.
In view of the above, an object of the present invention is to provide equipment that is stably operated by a power system by carrying a fuel cell and plural secondary cells.